Creation of pixel-by-pixel gray scale in bistable AC plasma (ACP) displays and DC plasma displays modified to provide bistability has been both studied and demonstrated over the last 20 years. Moreover, full color plasma displays employ pixel-by-pixel gray scale within each color channel. Although the concept has been demonstrated several times, it has been difficult to implement as a product because adequate drive systems were not able to avoid flicker and operate with real time non-interlaced digitized video sources such as VGA.
An early development model, when operated at 30 Hz update and with sequential pixel row scan, has especially noticeable flicker with still frame video and computer generated images. Most prior art gray scale plasma display demonstrations are either not capable of video rate update, or are specifically for broadcast video. In the first case, flicker may be avoided at the expense of not having real time video capability. In the second case, the operation with continuously changing video images tends to mask flicker. In any case, 30 Hz update operation on the ACP display does not sufficiently avoid flicker in static images, although it has been tolerated as an NTSC standard for CRTs. IBM's recently introduced 8514 and 8515 VGA monitors are based on a frame rate of 43.5 Hz for flickerless interlaced operation (Reference Computer Technology 30 view, August 1990, Flicker Free VGA Can Increase User's Productivity). This invention uses 46 Hz (or greater) interlaced update of the display in addition to nonsequential row scan to avoid flicker.
The bistable ACP display is currently produced by several organizations in Europe, Japan and the U.S., each organization making its own versions/configurations of the basic ACP technology. The basic technology incorporates neon gas mixtures as the display medium in the cavity where the matrix imposes pixel-by-pixel control voltages. The matrix may be located on one substrate or on two opposing substrates.
The neon gas mixtures used in ACP displays has certain physical response times which must be accommodated by all electronic drive systems:
1) The neon gas ion mobility is such that 5 microseconds must be allowed after each gas discharge for the ions to be redistributed for bistability in the cell. PA1 2) The erase phenomenon whereby a partial discharge is invoked requires at least 3.5 microseconds duration at discharge cell zero potential. PA1 1) Less circuitry, which results from the invention's unique application of standard high density memory architecture, and from the invention's unique panel waveform; allows a more compact display with less power dissipation, higher reliability and more cost effectivity. PA1 2) Fewer architecture functions, which result from the invention's unique application of standard high density memory architecture, and from the invention's unique panel waveform; allows more pixel data throughput for higher speed operation necessary to avoid flicker and to accept real time non-interlaced video.
ACP displays generally have interlaced electrodes which form the X-axis and Y-axis matrix lines: every other electrode is brought out to the edges of the panel so that there is a set of even connections (0, 2, 4, 6 . . .) and odd connections (1, 3, 5, 7 . . .) at the top and bottom respectively, and at the left and right sides, respectively. This electrode connection implementation has been employed to reduce the resolution requirements for drive system interconnect.